By Mark Ward BBC News Online technology correspondent

Bishop: Interactive books present new challenges

New Zealand researchers have developed a way to overlay detailed animations and images on textbooks, children's picture books and any other title that uses illustrations.

The 3D images are seen via a handheld viewer that watches where a reader is looking.

With a flick of a switch the viewer can also plunge readers into an immersive virtual world that lets them explore the book's subject in more depth.

Pictures and pages

The combined book and reader system has been developed by Dr Mark Billinghurst and colleagues at New Zealand's Human Interface Technology Lab (HIT Lab).

The viewer resembles a pair of spectacles on a stick or hi-tech opera glasses and is held in front of the eyes while a book is read or paged through.

Between the lenses is a camera that watches where they are looking.

Interaction is via hi-tech opera glasses

Software on an associated PC looks for distinctive features on the page to help spot what a reader is looking at.

"It then draws the computer graphics from exactly the same viewpoint," said Dr Billinghurst who heads the HIT Lab.

One of the early uses of the system has been to turn some of the books of writer and illustrator Gavin Bishop into animated works.

One of the first of his books to get the treatment was called Giant Jimmy Jones.

Turning this into an animated story presented Mr Bishop with some novel problems, said Dr Billinghurst.

"He's never had to think about what the Giant looks like from behind," said Dr Billinghurst, "it's exposing him to a new medium."

Immersive experience

The lab has also prepared immersive VR sequences for a textbook all about human anatomy.

In one section of the book readers could look at a 3D model of the heart.

"You can get God's eye view if you want," said Dr Billinghurst, "or you can go in and be part of the scene."

"You can flip a switch and transition into an immersive VR experience," he said. "You can fly inside and see what it feels like to be a blood corpuscle going through the heart."

The combined viewing and reading system, called the Magic Book, has already been used in some museums and public spaces in New Zealand.

Exhibits using the Magic Book technology have also been installed in Australia's Science Museum.